System and method for monitoring quality control of chemical mechanical polishing pads

ABSTRACT

The present invention provides a method for predicting a performance characteristic of a chemical mechanical polishing (CMP) pad. The method comprises providing a CMP pad having a polishing surface and measuring a frictional property of the polishing surface. The method further includes estimating a performance characteristic of the CMP pad based on the frictional property. Other aspects of the present invention include a quality control system for monitoring chemical mechanical polishing pad performance.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 60/536,136 entitled, “SYSTEM AND METHOD FOR MONITORING QUALITY CONTROL OF CHEMICAL MECHANICAL POLISHING PADS,” filed on Feb. 5, 2004, and incorporated by reference as if reproduced herein in its entirety.

TECHNICAL FIELD OF THE INVENTION

The present invention is directed to a method and a system for estimating a chemical mechanical polishing pad's performance characteristics based on the frictional properties of the polishing pad.

BACKGROUND OF THE INVENTION

Chemical mechanical polishing (CMP) has been successfully used for planarizing both metal and dielectric films. In one plausible mechanism of planarizing, the polishing process is thought to involve intimate contact between high points on a wafer surface and a polishing pad material in the presence of slurry. In this scenario, corroded materials, produced from reactions between the slurry and wafer surface being polished, are removed by shearing at the pad-wafer interface. The elastic properties of pad material significantly influence the final planarity and polishing rate. In turn, the elastic properties are a function of both the intrinsic polymer and its foamed structure.

Despite considerable effort to produce polishing pads with identical polishing characteristics, there are variations from pad to pad. This, in turn, causes undesirable variations in the extent of material removed, or in the planarity, of the wafer surfaces being polished. It would be highly desirable to be able to predict the performance characteristics of polishing pads a priori, that is, before it is used for polishing or during polishing itself. This goal has proven difficult to achieve, however.

Historically, polyurethane-based polishing pads have been used for CMP because of their high strength, hardness, modulus and high elongation at break. Because the performance characteristics of polyurethane-based pads change as the pad decomposes, it has proven difficult to predict the polishing characteristics of polishing pad prior to, or during, their use. While polyurethane-based pads can achieve both good uniformity and efficient topography reduction, their ability to rapidly and uniformly remove surface materials declines as a function of use. The decline in the polishing performance of polyurethane-based pads has been attributed to changes in the mechanical response of the pad under conditions of critical shear. It is generally believed that the loss in functionality of polyurethane-based CMP pads is due to pad decomposition from the interaction between the pad and the slurries used in the polishing. Additionally, decomposition produces a surface modification in and of itself in the case of the polyurethane pads which can be detrimental to uniform polishing.

Traditional measures to maintain quality control of polishing have been directed to intermittently testing individual wafers after being polished. For instance, post-polishing measurements can be used to determine if material removal rates and surface uniformity remain within an acceptable range. If the tolerance range is exceeded, then the polishing pad is either reconditioned or replaced. Polyurethane pads generally require a break-in period before polishing, in addition to the reconditioning and retreatment after a period of use. Moreover, it is often also necessary to keep traditional pads wet while the polishing equipment is in idle mode. These characteristics undesirably reduce the overall efficiency of CMP when using polyurethane or similar conventional pads.

Accordingly, what is needed is a method and system of estimating the performance characteristics of CMP polishing pads, and a system of implementing the method so as to provide more consistent polishing.

SUMMARY OF THE INVENTION

To address the above-discussed deficiencies of the prior art, the present invention provides in one embodiment, a method for predicting a performance characteristic of a CMP pad. The method comprises providing a CMP pad having a polishing surface and measuring a frictional property of the polishing surface. The method further comprises estimating a performance characteristic of the CMP pad based on the frictional property.

Another embodiment of the present invention is directed to a quality control system for monitoring CMP pad performance. The system comprises a detector configured to determine a frictional property of a surface of a CMP pad. The system further comprises a controller coupled to the detector, the controller configured to estimate a performance characteristic of the CMP pad surface based on the frictional property.

The foregoing has outlined preferred and alternative features of the present invention so that those skilled in the art may better understand the detailed description of the invention that follows. Additional features of the invention will be described hereinafter that form the subject of the claims of the invention. Those skilled in the art should appreciate that they can readily use the disclosed conception and specific embodiment as a basis for designing or modifying other structures for carrying out the same purposes of the present invention. Those skilled in the art should also realize that such equivalent constructions do not depart from the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

FIG. 1 illustrates by flow diagram, an exemplary method for predicting a performance characteristic of a chemical mechanical polishing pad;

FIG. 2 presents an exemplary quality control system for monitoring chemical mechanical polishing pad performance;

FIG. 3 presents exemplary data showing the change in relative Blanket Tungsten Removal Rate (WRR) and the Mean Static Coefficient of Friction (SCOF) obtained for thermoplastic foam polishing pads as a function of coating time with TEOS; and

FIG. 4 presents exemplary data showing the relationship between Blanket Tungsten Removal Rate (W-RR) and Mean Static Coefficient of Friction (SCOF) and Dynamic Coefficient of Friction (DCOF) for exemplary thermoplastic foam polishing pads.

DETAILED DESCRIPTION

The present invention benefits from discoveries made during the course of characterizing the physical properties of novel polishing pads. The pad's frictional properties were determined as part of a battery of physical measurements to characterize the polishing pads. It was accidentally discovered that the frictional properties of the polishing pad's surface had a significant correlation with the polishing properties of individual polishing pads. This, in turn, led to the realization that surface frictional properties can be generally used to predict the performance characteristics of chemical mechanical polishing pads. The ability to make such a priori predictions allows one to eliminate pads whose predicted performance is outside of an acceptable tolerance, or to modify polishing parameters to compensate for variations in polishing performance.

The term performance characteristic as used herein refers to any conventional quantitative measure of polishing performance, including but not limited to: removal rate of material from a substrate, within-substrate polishing uniformity (also commonly referred to as within-wafer-non-uniformity, WIWNU), or the extent or dishing, erosion, or defects on a polished substrate. The term substrate as used herein refers to any material upon which a microelectronic device can be formed, such as a semiconductor device on a silicon wafer, and well as metal layers, barrier layers, dielectric films, or combinations thereof, or other material layers formed on the substrate's surface.

One aspect of the present invention, illustrated by the exemplary flow diagram in FIG. 1, is a method 100 for predicting a performance characteristic of a CMP pad. The method 100 comprises in step 105, providing a CMP pad having a polishing surface. The method 100 further comprises in step 110, measuring a frictional property of the CMP pad's polishing surface. The method 100 also comprises estimating, in step 115, a performance characteristic of the CMP pad, based on the frictional property.

The measurement of the CMP pad's frictional properties can be performed at any number of different times. In certain preferred embodiments, the frictional property of the CMP pad's polishing surface is measured in step 120 shortly after pad manufacture. In some advantageous embodiments, the frictional property of the CMP pad is measured in step 125, prior to use for CMP. In some case, for example, the frictional property is measured in step 125 after pad conditioning and just prior to CMP. In other advantageous embodiments, the frictional property is measured in step 130, during CMP of a substrate surface.

Any conventional measurement can be used to quantify the CMP pad's frictional properties in step 110. In some preferred embodiments, for instance, the frictional property measured in any of steps 120, 125, 130 is a coefficient of friction (COF). The COF can comprise a static COF, a dynamic COF or both, measured by any number of conventional procedures well known to those of ordinary skill in the art. Some preferred methods of measuring the static COF and dynamic COF are presented in the Example section to follow. In some cases, for example, the frictional property is measured using a detector comprising a tribometer. In some preferred embodiments, a static COF is measured in step 120 after pad manufacture or in step 125 prior to polishing. In other preferred embodiments, the dynamic COF is measured in step 125 or step 130, before or during polishing, respectively.

In some preferred embodiments of the method 100, estimating the performance characteristic in step 115 comprises comparing, in step 135, the frictional property to a database. The database provides a functional relationship between the frictional property and the performance characteristic. The functional relationship is then used to predict a performance characteristic, based on the frictional property for a particular pad.

By way of example, the database can comprise the removal rate of tungsten from a substrate surface for a plurality of CMP pads having different COFs. Such a database can be empirically determined in step 140 by producing a plurality of CMP pads having surfaces with different COFs. The COF of the pad's surface can be altered by changing one or more of: the composition of the material comprising the polishing pad, the number or size of concave cells on the thermoplastic foam polishing body of the pad, or the composition of the polishing agent coating the interior surface of the concave cells of the thermoplastic foam. For example, the composition of the polishing agent can be altered by changing the duration for which the interior surface of the concave cells is coated with the polishing agent. In some instances, the longer the coating time, the greater the COF of the pad surface.

Continuing with the determination of the database in step 140, a set of polishing pads having different frictional properties , e.g., COFs, is used to polish tungsten-coated test substrate wafers under standardized polishing conditions. The standardized polishing conditions can comprise the polishing slurry composition, slurry flow rate, the down force, table speed, backside pressure, carrier speed of a rotational polishing platform coupled to the polishing pad, or any other condition that effect the performance characteristic of interest. After a period of polishing, the test substrate wafers are then measured to determine the performance characteristic, such as tungsten removal rate.

Conventional graphical or statistical procedures are then used to elucidate the causal relationship between the frictional property and the performance characteristic in step 145. For instance, the relationship between the COF and a tungsten removal rate can be represented graphically, such as illustrated in the Example section below, or by one or more linear or nonlinear equations that are fit to the database using linear or non-linear regression analysis. Such graphs or equations can then be used to predict the tungsten removal rate of an individual CMP pad based on the COF for a particular pad, as per step 115.

Of course, the performance characteristic estimated in step 115 can comprise the rate of removal of any number of materials on the substrate surface. Such materials include silicon wafers having a metal layer comprising a refractory metal, such as tungsten, nickel, or aluminum, or a noble metal, such as copper, gold, platinum, iridium, ruthenium, cobalt, osmium or silver, and combinations thereof. Such materials also include a dielectric layer, such as silicon oxide or a barrier layer, such as tantalum, metal silicides, such as nickel silicide, or polysilicon and combinations thereof. Alternatively, the performance characteristic can be some other indicator of polishing such as the WIWNU of a substrate's surface after CMP using the pad, or other indicators such as dishing, erosion, or defectivity.

In some preferred embodiments, the performance characteristic is estimated in step 115 using a controller comprising a computer system. The computer system can comprise a memory unit capable of storing the database determined in step 140 and processing circuitry configured to determine the causal relationship between the frictional property and the performance characteristic from the database as per step 145, and compare the measured frictional property of the instant pad to the database as per step 135.

In some embodiments of the method 100, the predicted performance characteristic is used to accept or eliminate CMP pads, in step 150, whose predicted performance is outside of an acceptable tolerance. For example, the controller, upon estimating that a performance characteristic for a pad is outside of an acceptable tolerance, would signal a pad manufacturing system in step 150 to reject the pad for packaging and shipping to an end-user.

In other embodiments, the predicted performance characteristic is used to modify polishing parameters, in step 160, to compensate for predicted deviations from a desired polishing performance. For example, the controller, upon estimating that a performance characteristic for a pad is outside of an acceptable tolerance, may signal a polishing system to extend a polishing time because the predicted removal rate is below an acceptable tolerance range. As a further example, in some preferred embodiments the controller adjusts one or more polishing parameter for a subsequent batch of wafers based on said estimated performance characteristic for a previous batch of wafers.

While the method 100 can be applied to estimate the polishing parameters of any conventional CMP pad, the method is particularly advantageous when the CMP pad provided in step 105 comprises a polishing body comprising a thermoplastic foam substrate. While not limiting the scope of the present invention by theory, it is believed that the static COF provides a measure of the inherent physical properties of thermoplastic foam substrates. The dynamic COF is believed to provide a measure of the hydrodynamic properties of the CMP pads comprising such thermoplastic foam substrates.

In particular, certain preferred embodiments of the polishing pad provided in step 105 comprises a thermoplastic foam substrate having a polishing surface comprising concave cells. In other embodiments, a polishing agent coats an interior surface of the concave cells of the polishing pad. Some advantageous polishing pads are described in: U.S. patent application Ser. No. 10/000,101, entitled, “THE SELECTIVE CHEMICAL-MECHANICAL POLISHING PROPERTIES OF A CROSS LINKED POLYMER AND SPECIFIC APPLICATIONS THEREFOR,” to Yaw S. Obeng and Edward M. Yokely, filed Oct. 24, 2001; U.S. Pat. No. 6,579,604, entitled “A METHOD OF ALTERING AND PRESERVING THE SURFACE PROPERTIES OF A POLISHING PAD AND SPECIFIC APPLICATIONS THEREFOR,” to Yaw S. Obeng and Edward M. Yokely; its continuation in part, U.S. Pat. No. 6,706,383, entitled “A POLISHING PAD SUPPORT THAT IMPROVES POLISHING PERFORMANCE AND LONGEVITY” to Yaw S. Obeng and Peter A. Thomas; its continuation application Ser. No. 10/641,866, filed Aug. 15, 2003; and its continuation-in-part U.S. patent application Ser. No. 10/___,___, entitled, “A POLISHING PAD WITH HIGH SELECTIVITY FOR BARRIER POLISHING,” to Yaw S. Obeng, filed Oct. 10, 2004, all of which are incorporated by reference herein in their entirety.

In some preferred embodiments, for example, the thermoplastic foam substrate provided in step 105 can comprise cross-linked polyolefins, such as polyethylene, polypropylene, and combinations thereof. In some cases, the thermoplastic foam substrate comprises a closed-cell foam of crosslinked homopolymer or copolymers. Examples of closed-cell foam crosslinked homopolymers comprising polyethylene (PE) include: Volara™ and Volextra™ from Voltek (Lawrence, Mass.); Aliplast™, from JMS Plastics Supply, Inc. (Neptune, N.J.); or Senflex T-Cell™ (Rogers Corp., Rogers, Conn.). Examples of closed-cell foams of crosslinked copolymers comprising polyethylene and ethylene vinyl acetate (EVA) include: Volara™ and Volextra™ (from Voltek Corp.); Senflex EVATM (from Rogers Corp.); and J-foam™ (from JMS Plastics JMS Plastics Supply, Inc.).

In other preferred embodiments, the closed-cell thermoplastic foam substrate provided in step 105 comprises a blend of crosslinked ethylene vinyl acetate copolymer and a low-density polyethylene copolymer (preferably between about 0.1 and about 0.3 gm/cc). In yet other advantageous embodiments, the blend has a ethylene vinyl acetate:polyethylene weight ratio between about 1:9 and about 9:1. In certain preferred embodiments, the blend comprises ethylene vinyl acetate ranging from about 5 to about 45 wt %, preferably about 6 to about 25 wt % and more preferably about 12 to about 24 wt %. Such blends are thought to be conducive to the desirable production of concave cells having a small size as further discussed below. In still more preferred embodiments, the blend has a ethylene vinyl acetate:polyethylene weight ratio between about 0.6:9.4 and about 1.8:8.2. In even more preferred embodiments, the blend has an ethylene vinyl acetate:polyethylene weight ratio between about 0.6:9.4 and about 1.2:8.8.

In some instances, as further disclosed in the above-cited U.S. Pat. No. 6,706,383, the thermoplastic foam substrate provided in step 105 has cells formed throughout the substrate. In certain preferred embodiments, the cells are substantially spherical. In other preferred embodiments, the size of the cells are such that, on skiving the substrate, the open concave cells at the surface of the substrate have an average size between about 100 microns and 600 microns. The average size of the concave cells ranges from about 100 to about 350 microns, preferably about 100 to about 250 microns and more preferably about 115 to about 200 microns. Cell size may be determined using standard protocols, developed and published by the American Society for Testing and Materials (West Conshohocken, Pa.), for example, such as ASTM D3576, incorporated herein by reference.

The polishing agent can comprise one or more ceramic compounds or one or more organic polymers, resulting from the grafting of the secondary reactants on the substrate's surface, as disclosed in the above-cited U.S. Pat. No. 6,579,604. In some preferred embodiments, the polishing agent comprises an inorganic metal oxide that includes nitrides or carbides, as disclosed in U.S. patent application Ser. No. 10/685,219 entitled, “A CORROSION RETARDING POLISHING SLURRY FOR THE CHEMICAL MECHANICAL POLISHING OF COPPER SURFACES” to Yaw S. Obeng, filed on Oct. 14, 2003, and incorporated herein by reference in its entirety.

In some preferred embodiments, the ceramic polishing agent can comprise an inorganic metal oxide resulting when an oxygen-containing organometallic compound is used as the secondary reactant to produce a grafted surface. For example, the secondary plasma mixture may include a transition metal such as titanium, manganese, or tantalum. However, any metal element capable of forming a volatile organometallic compound, such as a metal ester containing one or more oxygen atoms, and capable of being grafted to the polymer surface is suitable. Silicon may also be employed as the metal portion of the organometallic secondary plasma mixture. In these embodiments, the organic portion of the organometallic reagent may be an ester, acetate, or alkoxy fragment. In preferred embodiments, the polishing agent is selected from a group of ceramics consisting of Silicon Oxides and Titanium Oxides, such as Silicon Dioxide and Titanium Dioxide; Tetraethoxy Silane (TEOS) Polymer; and Titanium Alkoxide Polymer.

Another aspect of the present invention is a quality control system for monitoring CMP pad performance. FIG. 2 presents an exemplary quality control system 200 that applies the principles of the present invention. The system 200 can be configured to implement any of the embodiments of the method for predicting a performance characteristic of a chemical mechanical polishing pad, such as illustrated in FIG. 1 and described above.

The system 200 comprises a detector 210 configured to determine a frictional property of a CMP pad 220. The term detector 210, as used herein, refers to any device capable of quantifying the frictional properties of a polishing pad surface 225. In certain preferred embodiments, for example, the detector 210 comprises a tribometer configured to measure static or dynamic COF, or both.

The system 200 also comprises a controller 230 coupled to the detector 210 and configured to estimate a performance characteristic of the CMP pad 220 based on the frictional property of the pad's surface 225. In some embodiments, the controller 230 comprises an input device 235 configured to receive a signal 240 from the detector 210, the signal 240 comprising information about the pad's frictional property. The input device 235 is further coupled to a computer system 250 of the controller 230.

The computer system 250 can comprise any conventional processing devices well known to those skilled in the art, to facilitate performing operations needed to estimate the pad's performance characteristic. Preferred embodiments of the computer system 250 comprise a central processing unit coupled via a bus to a memory. The computer system 250 further comprises storage circuitry 255 comprising various peripheral devices well known to one skilled in the art for storing and providing data. Non-limiting examples of storage circuitry 255 include floppy, hard, CD or optical drives. The storage circuitry 255 can store a plurality of files, including the above-described database relating the frictional property to a performance characteristic, and a program file comprising a conventional programming language.

The computer system 250 is programmed to estimate a performance characteristic by applying the program file to the database, provided by the storage circuitry 255, and the frictional property, provide by the input device 235. For instance, information in the program file and the database can be loaded into the memory of the computer system, thereby programming the computer processor to estimate the performance characteristic based on the frictional property, in accordance with step 115 in FIG. 1.

The controller 230 can further comprise an output device 260 coupled to the computer system 240, thereby coupling the controller 230 to other components of the quality control system 200. In some instances, for example, the output device 260 couples the controller 230 to a pad manufacturing apparatus 270 of the quality control system 200. In some preferred embodiments, the computer system 240 is further programmed to send an alert signal 275, via the output device 260, to the manufacturing apparatus 270. The alert signal 275 instructs the manufacturing apparatus 270 to accept or reject the polishing pad 220, depending on whether or not the estimated performance characteristic is within or outside of a predefined range.

In other embodiments, the output device 260 couples the controller 230 to a polishing apparatus 280 of the quality control system 200. In some preferred embodiments, the computer system 240 is further programmed to send a control signal 285, via the output device 260, to the polishing apparatus 280. The control signal 285 instructs the polishing apparatus 280 to retain or modify any number of polishing parameters depending on whether or not the estimated performance characteristic is within or outside of a predefined range. Non-limiting examples of polishing parameters that can be modified include: a rotational speed of a platen of the polishing apparatus 280 that holds the polishing pad 220; a rotational speed of a carrier head of the polishing apparatus 280 that holds a substrate to be polished; a down force imparted by the carrier head when positioned against the polishing platen; or a duration of polishing time.

Having described the present invention, it is believed that the same will become even more apparent by reference to the following experiments. It will be appreciated that the experiments are presented solely for the purpose of illustration and should not be construed as limiting the invention. For example, although the experiments described below may be carried out in a laboratory setting, one skilled in the art could adjust specific numbers, dimensions and quantities up to appropriate values for a full-scale plant setting.

Experiments

Experiments were conducted to: 1) characterize the chemical composition of thermoplastic foam substrates coated with polishing agents as a function of coating time; 2) characterize the mechanical properties of the foam substrate coated with polishing agents; and 3) measure the polishing properties of the polishing pads coated with the polishing agent.

A thermoplastic foam substrate was formed into circular polishing pads of approximately 120 cm diameter of about 0.3 cm thickness. The commercially obtained thermoplastic foam substrate (J-foam from JMS Plastics, Neptune N.J.), designated as “J-60SE,” comprised a blend of about 18% EVA, about 16 to about 20% talc, and balance polyethylene and other additives, such as silicates, present in the commercially provided substrate. The J-60 sheets were skived with a commercial cutting blade (Model number D5100 K1, from Fecken-Kirfel, Aachen, Germany). The sheets were then manually cleaned with an aqueous/isopropyl alcohol solution.

The J-60SE substrate was then coated with a polishing agent comprising Tetraethoxy Silane (TEOS), by placing the skived substrate into a reaction chamber of a conventional commercial Radio Frequency Glow Discharge (RFGD) plasma reactor having a temperature controlled electrode configuration (Model PE-2; Advanced Energy Systems, Medford, N.Y.). The plasma treatment of the substrate was commenced by introducing the primary plasma reactant, Argon, for 30 seconds within the reaction chamber maintained at 350 mTorr. The electrode temperature was maintained at 30° C., and a RF operating power of 300 Watts was used. Subsequently, the secondary reactant was introduced, for periods ranging from about 0 to about 45 minutes at 0.10 SLM, and comprising TEOS mixed with He or Ar gas. The amount of secondary reactant in the gas stream was governed by the vapor back-pressure (BP) of the secondary reactant monomer at the monomer reservoir temperature (MRT; 50±10° C.).

In some experiments the polishing properties of the J60SE polishing pads were examined by polishing wafers having an about 4000 Angstrom thick tungsten surface and an underlying about 250 Angstrom thick titanium nitride barrier layer. Tungsten polishing properties were assessed using a commercial polisher (Product No. EP0222 from Ebara Technologies, Sacramento, Calif.). Unless otherwise noted, the removal rate of tungsten polishing was assessed using a down force of about 25 kPa of substrate, table speed of about 100 to about 250 rpm. A conventional slurry (Product Number MSW2000, from Rodel, Newark Del.) adjusted to a pH of about 2 was used.

In other experiments, the static coefficient of friction (SCOF) of the polishing pads was measured before polishing using a hand-held tribometer (Heidon Tribogear μs Type 94i, Kett US, Villa Park, Calif.). The dynamic coefficient of friction (DCOF) was measured using a CETR CP-4 bench top CMP tester (CETR, Inc., Campbell, Calif.), under polishing conditions substantial similar to that described above. The DCOF was filtered using the wavelet transform technique.

FIG. 3 illustrates the relationship between the Relative Blanket Tungsten Removal Rate (W-RR) and the Static Coefficient of Friction (SCOF) for exemplary thermoplastic foam substrates subjected to different periods of coating times with TEOS. Both the W-RR and COF increase with increased coating times up to 30 minutes, which in turn, corresponds to an increase the thickness of polishing agent on the polishing surface of the pad.

FIG. 4 shows the relationship between Blanket Tungsten Removal Rate (W-RR) and mean Static Coefficient of Friction (SCOF) and mean Dynamic Coefficient of Friction (DCOF) for exemplary thermoplastic foam polishing pads. There was a strong linear correlation between W-RR and SCOF (r=0.81). A similar high correlation was observed between SCOF and the removal rate of a silicon dioxide layer (r=−0.92).

Although the present invention has been described in detail, those skilled in the art should understand that they can make various changes, substitutions and alterations herein without departing from the scope of the invention. 

1. A method for predicting a performance characteristic of a chemical mechanical polishing pad, comprising: providing a chemical mechanical polishing (CMP) pad having a polishing surface; measuring a frictional property of said polishing surface; and estimating a performance characteristic of said CMP pad based on said frictional property.
 2. The method as recited in claim 1, wherein said frictional property comprises a static coefficient of friction.
 3. The method as recited in claim 1, wherein said frictional property comprises a dynamic coefficient of friction.
 4. The method as recited in claim 1, wherein said CMP pad comprises a thermoplastic foam substrate comprising a blend of a crosslinked ethylene vinyl acetate copolymer and a low-density polyethylene copolymer, and said polishing surface comprises concave cells.
 5. The method as recited in claim 1, wherein estimating said performance characteristic comprises comparing said frictional property to a database, wherein said database provides a functional relationship between said frictional property and said performance characteristic.
 6. The method as recited in claim 1, wherein said performance characteristic comprises a removal rate of a material from a substrate.
 7. The method as recited in claim 6, wherein said material comprises a metal layer, a barrier layer, a dielectric films, or combinations thereof.
 8. The method as recited in claim 7, wherein said metal layer comprises a refractory metal or a noble metal.
 9. The method as recited in claim 1, wherein said performance characteristic comprises a within substrate uniformity.
 10. The method as recited in claim 1, wherein said frictional property is measured using a detector comprising a tribometer and said performance characteristic is estimated using a controller comprising a computer.
 11. A quality control system for monitoring chemical mechanical polishing pad performance, comprising: a detector configured to determine a frictional property of a surface of a chemical mechanical polishing (CMP) pad; and a controller coupled to said detector and configured to estimate a performance characteristic of said CMP pad surface based on said frictional property.
 12. The quality control system as recited in claim 11, wherein said frictional property comprises a static coefficient of friction.
 13. The quality control system as recited in claim 11, wherein said frictional property comprises a dynamic coefficient of friction.
 14. The quality control system as recited in claim 11, wherein said CMP pad comprises a thermoplastic foam substrate comprising a blend of a crosslinked ethylene vinyl acetate copolymer and a low-density polyethylene copolymer, and said polishing surface comprises concave cells.
 15. The quality control system as recited in claim 11, wherein said controller adjusts one or more polishing parameter of a polishing apparatus coupled to said controller, based on said estimated performance characteristic.
 16. The quality control system as recited in claim 15, wherein said controller adjusts one or more polishing parameter for a subsequent batch of wafers based on said estimated performance characteristic for a previous batch of wafers.
 17. The quality control system as recited in claim 15, wherein said polishing parameter comprises a rotational speed of a platen of said polishing apparatus.
 18. The quality control system as recited in claim 15, wherein said polishing parameter comprises a rotational speed of a carrier head of said polishing apparatus.
 19. The quality control system as recited in claim 15, wherein said polishing parameter comprises a down-force imparted by a carrier head against said CMP pad surface.
 20. The quality control system as recited in claim 15, wherein said polishing parameter comprises a duration of polishing.
 21. The quality control system as recited in claim 11, wherein said controller rejects a chemical mechanical polishing pad produced by a manufacturing apparatus coupled to said controller based, on said estimated performance characteristic. 